(1) Field of the Invention
This invention relates to a metal vapor laser generating apparatus utilizing a cataphoresis effect, and more particularly, to a laser generating apparatus of a long life and high efficiency.
(2) Description of the Prior Art
In a prior art metal vapor laser generating apparatus utilizing a cataphoresis effect, a branch tube housing a metal is disposed adjacent to the anode of a discharge tube housing rare gas. The metal is evaporated by heating and, then, injected into a positive column forced in the discharge tube. The evaporated metal introduced into the positive column is ionized and flows toward the cathode, thereby forming a stream of ionized metal within the positive column.
In order to form a uniform stream of ionized metal within the discharge tube by cataphoresis effect, it is necessary to keep the metal vapor pressure on the side of the cathode lower than that on the side of the anode. To this end, some of the prior apparatus are equipped with a branch tube housing an adsorbent, which is disposed near the cathode, so as to allow the adsorbent to trap the ionized metal. In an apparatus of this construction, however, only a small portion of the ionized metal flows into the branch tube; a majority of the ionized metal flows to reach and sputter the cathode, resulting in a shortened life of the laser tube. An additional problem inherent in the prior apparatus is that the evaporated metal, when not trapped by the adsorbent, is accumulated around the cathode and absorbs light, leading to a decreased laser oscillation efficiency.